A flat-rate telecommunication service is a system where a subscriber can use a telecommunication service with unlimited minutes at a fixed cost. A billing system opposite to the flat-rate system is a minute-rate system, where the subscriber is billed based on the minutes for which he/she uses the telecommunication service.
The flat-rate telecommunication system has an advantage that it can relieve subscribers from the burden of telecommunication service charge by charging them only a predetermined amount of money. However, there is a problem that it is hard to determine a flat rate of a telecommunication service that both service provider and subscribers can accept. Conventional methods for charging a flat rate do not reflect the subscriber's service usage history at all and charge all the subscribers the same flat rate for the service, collectively.
To solve the problem, researchers are studying to develop a method for calculating a flat rate based on the previous telecommunication service usage history of each user. According to the method, different flat rate is imposed to each subscriber and subscribers pay as much as a predetermined flat rate for their using the telecommunication service, no matter how long they use the service.
However, this method also has a problem that the subscriber should pay the determined flat rate, even when the subscriber uses the telecommunication service far shorter than the time of his previous telecommunication service usage history.
This is unreasonable to bill the flat rate, which is higher than the subscriber has actually used, to the subscriber who has used the telecommunication service much less than usual. This problem may cause decrease in the number of subscribers to the telecommunication service.